WASHINGTON (Reuters) - The Pentagon is about to roll out an expanded effort to safeguard its contractors from hackers and is building a virtual firing range in cyberspace to test new technologies, according to officials familiar with the plans, as a recent wave of cyber attacks boosts concerns about U.S. vulnerability to digital warfare. (http://feeds.feedburner.com/~ff/reuters/topNews?d=yIl2AUoC8zA) (http://feeds.feedburner.com/~ff/reuters/topNews?i=TdRZdbjL7DQ:g5vZF0s0mOU:V_sGLiPBpWU) (http://feeds.feedburner.com/~ff/reuters/topNews?i=TdRZdbjL7DQ:g5vZF0s0mOU:-BTjWOF_DHI) (http://feeds.feedburner.com/~r/reuters/topNews/~4/TdRZdbjL7DQ)